Screen pixalating only with driver installation on brand new computer

I just put together a new Gigabyte 2004 rz series mobo with an athalon 3000+ xp processor and a Xfx geforce 6600gt vid card. Got a gig of ram and started up perfectly first try. Problem is when i load the drivers for the video card, the screen looks like your psp when you threw it at a wall and some of the crystals died in the display. Pixels are missin on the screen and opening new windows just makes it worse. I unihnstalled the drivers and the screen looked crystal clear again. Being that i built the computer for World of Warcraft, i kinda need those drivers to be in place for it to work properly :/ please offer any advice you might have, thanks.